Config Package

pkg/config/README.md

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+# ResolveSpec Configuration System
+
+A centralized configuration system with support for multiple configuration sources: config files (YAML, TOML, JSON), environment variables, and programmatic configuration.
+
+## Features
+
+- **Multiple Config Sources**: Config files, environment variables, and code
+- **Priority Order**: Environment variables > Config file > Defaults
+- **Multiple Formats**: YAML, TOML, JSON supported
+- **Type Safety**: Strongly-typed configuration structs
+- **Sensible Defaults**: Works out of the box with reasonable defaults
+
+## Quick Start
+
+### Basic Usage
+
+```go
+import "github.com/heinhel/ResolveSpec/pkg/config"
+
+// Create a new config manager
+mgr := config.NewManager()
+
+// Load configuration from file and environment
+if err := mgr.Load(); err != nil {
+    log.Fatal(err)
+}
+
+// Get the complete configuration
+cfg, err := mgr.GetConfig()
+if err != nil {
+    log.Fatal(err)
+}
+
+// Use the configuration
+fmt.Println("Server address:", cfg.Server.Addr)
+```
+
+### Custom Configuration Paths
+
+```go
+mgr := config.NewManagerWithOptions(
+    config.WithConfigFile("/path/to/config.yaml"),
+    config.WithEnvPrefix("MYAPP"),
+)
+```
+
+## Configuration Sources
+
+### 1. Config Files
+
+Place a `config.yaml` file in one of these locations:
+- Current directory (`.`)
+- `./config/`
+- `/etc/resolvespec/`
+- `$HOME/.resolvespec/`
+
+Example `config.yaml`:
+
+```yaml
+server:
+  addr: ":8080"
+  shutdown_timeout: 30s
+
+tracing:
+  enabled: true
+  service_name: "my-service"
+
+cache:
+  provider: "redis"
+  redis:
+    host: "localhost"
+    port: 6379
+```
+
+### 2. Environment Variables
+
+All configuration can be set via environment variables with the `RESOLVESPEC_` prefix:
+
+```bash
+export RESOLVESPEC_SERVER_ADDR=":9090"
+export RESOLVESPEC_TRACING_ENABLED=true
+export RESOLVESPEC_CACHE_PROVIDER=redis
+export RESOLVESPEC_CACHE_REDIS_HOST=localhost
+```
+
+Nested configuration uses underscores:
+- `server.addr` → `RESOLVESPEC_SERVER_ADDR`
+- `cache.redis.host` → `RESOLVESPEC_CACHE_REDIS_HOST`
+
+### 3. Programmatic Configuration
+
+```go
+mgr := config.NewManager()
+mgr.Set("server.addr", ":9090")
+mgr.Set("tracing.enabled", true)
+
+cfg, _ := mgr.GetConfig()
+```
+
+## Configuration Options
+
+### Server Configuration
+
+```yaml
+server:
+  addr: ":8080"              # Server address
+  shutdown_timeout: 30s       # Graceful shutdown timeout
+  drain_timeout: 25s          # Connection drain timeout
+  read_timeout: 10s           # HTTP read timeout
+  write_timeout: 10s          # HTTP write timeout
+  idle_timeout: 120s          # HTTP idle timeout
+```
+
+### Tracing Configuration
+
+```yaml
+tracing:
+  enabled: false                                  # Enable/disable tracing
+  service_name: "resolvespec"                     # Service name
+  service_version: "1.0.0"                        # Service version
+  endpoint: "http://localhost:4318/v1/traces"     # OTLP endpoint
+```
+
+### Cache Configuration
+
+```yaml
+cache:
+  provider: "memory"  # Options: memory, redis, memcache
+
+  redis:
+    host: "localhost"
+    port: 6379
+    password: ""
+    db: 0
+
+  memcache:
+    servers:
+      - "localhost:11211"
+    max_idle_conns: 10
+    timeout: 100ms
+```
+
+### Logger Configuration
+
+```yaml
+logger:
+  dev: false    # Development mode (human-readable output)
+  path: ""      # Log file path (empty = stdout)
+```
+
+### Middleware Configuration
+
+```yaml
+middleware:
+  rate_limit_rps: 100.0       # Requests per second
+  rate_limit_burst: 200        # Burst size
+  max_request_size: 10485760   # Max request size in bytes (10MB)
+```
+
+### CORS Configuration
+
+```yaml
+cors:
+  allowed_origins:
+    - "*"
+  allowed_methods:
+    - "GET"
+    - "POST"
+    - "PUT"
+    - "DELETE"
+    - "OPTIONS"
+  allowed_headers:
+    - "*"
+  max_age: 3600
+```
+
+### Database Configuration
+
+```yaml
+database:
+  url: "host=localhost user=postgres password=postgres dbname=mydb port=5432 sslmode=disable"
+```
+
+## Priority and Overrides
+
+Configuration sources are applied in this order (highest priority first):
+
+1. **Environment Variables** (highest priority)
+2. **Config File**
+3. **Defaults** (lowest priority)
+
+This allows you to:
+- Set defaults in code
+- Override with a config file
+- Override specific values with environment variables
+
+## Examples
+
+### Production Setup
+
+```yaml
+# config.yaml
+server:
+  addr: ":8080"
+
+tracing:
+  enabled: true
+  service_name: "myapi"
+  endpoint: "http://jaeger:4318/v1/traces"
+
+cache:
+  provider: "redis"
+  redis:
+    host: "redis"
+    port: 6379
+    password: "${REDIS_PASSWORD}"
+
+logger:
+  dev: false
+  path: "/var/log/myapi/app.log"
+```
+
+### Development Setup
+
+```bash
+# Use environment variables for development
+export RESOLVESPEC_LOGGER_DEV=true
+export RESOLVESPEC_TRACING_ENABLED=false
+export RESOLVESPEC_CACHE_PROVIDER=memory
+```
+
+### Testing Setup
+
+```go
+// Override config for tests
+mgr := config.NewManager()
+mgr.Set("cache.provider", "memory")
+mgr.Set("database.url", testDBURL)
+
+cfg, _ := mgr.GetConfig()
+```
+
+## Best Practices
+
+1. **Use config files for base configuration** - Define your standard settings
+2. **Use environment variables for secrets** - Never commit passwords/tokens
+3. **Use environment variables for deployment-specific values** - Different per environment
+4. **Keep defaults sensible** - Application should work with minimal configuration
+5. **Document your configuration** - Comment your config.yaml files
+
+## Integration with ResolveSpec Components
+
+The configuration system integrates seamlessly with ResolveSpec components:
+
+```go
+cfg, _ := config.NewManager().Load().GetConfig()
+
+// Server
+srv := server.NewGracefulServer(server.Config{
+    Addr:            cfg.Server.Addr,
+    ShutdownTimeout: cfg.Server.ShutdownTimeout,
+    // ... other fields
+})
+
+// Tracing
+if cfg.Tracing.Enabled {
+    tracer := tracing.Init(tracing.Config{
+        ServiceName:    cfg.Tracing.ServiceName,
+        ServiceVersion: cfg.Tracing.ServiceVersion,
+        Endpoint:       cfg.Tracing.Endpoint,
+    })
+    defer tracer.Shutdown(context.Background())
+}
+
+// Cache
+var cacheProvider cache.Provider
+switch cfg.Cache.Provider {
+case "redis":
+    cacheProvider = cache.NewRedisProvider(cfg.Cache.Redis.Host, cfg.Cache.Redis.Port, ...)
+case "memcache":
+    cacheProvider = cache.NewMemcacheProvider(cfg.Cache.Memcache.Servers, ...)
+default:
+    cacheProvider = cache.NewMemoryProvider()
+}
+
+// Logger
+logger.Init(cfg.Logger.Dev)
+if cfg.Logger.Path != "" {
+    logger.UpdateLoggerPath(cfg.Logger.Path, cfg.Logger.Dev)
+}
+```